Magnetic seal for wafer containers

ABSTRACT

A wafer container with the door frame has a magnetic seal that encircles the periphery of the door and has a flexible portion extending laterally outwardly to engage a corresponding magnetic seal around the periphery of the door. Thus the door and container can be provided with a seal that is strong enough to exclude contaminants and also allows easy removal of the door either manually or by a robotic arm.

BACKGROUND OF THE INVENTION

This invention relates to enclosures. More particularly, it relates to sealable enclosure for holding wafers to be manufactured into semiconductors.

Semiconductor wafers are subjected to numerous steps during processing. This usually entails transporting a plurality of wafers from one workstation to another for processing by specialized equipment. As part of the processing procedure, wafers may be temporarily stored or shipped in containers to other plants or to end users. Such intra and extra movements may generate or expose the wafers to potential wafer ruining contaminants. In order to reduce the deleterious effect of contaminants on wafers, specialized containers have been developed to minimize the generation of contaminants and to isolate wafers from contaminants exterior to the containers. A principal feature common to these devices is that they are provided with removable doors or closures which seal or are sealed by tape or externally such as in plastic bagging.

As semiconductor integrated circuits have become smaller in scale, that is, as the number of circuits per unit area has increased, contaminants in the form of particulates have become more problematic. The size of particulates that can destroy a circuit has decreased and is approaching the molecular level. Particulate control is necessary during all phases of manufacturing, processing, transporting, and storage of semiconductor wafers. The industry is moving toward processing larger and larger wafers into semiconductors. Three hundred millimeter (300 mm) wafers are now commonplace.

Wafer carriers may be made of a variety of materials which in almost all cases today are comprised of thermoplastics. Early containers including, enclosures and closures, were made of highly moldable plastics such as polyethylene, see U.S. Pat. No. 4,248,346, and some held rigid h-bar carriers such as disclosed in U.S. Pat. No. 5,273,159, and some comprise polycarbonate enclosure portions with molded in slots and with softer more resilient covers. An example is disclosed in U.S. Pat. No. 5,586,658.

Such containers typically relied on an enclosure portion that engaged the flexible cover for providing the sealing of the container. Other containers, primarily for use within semiconductor fabrication facilities, have both a rigid door to enclosure portion seal provided by an elastomeric seal and also may have the capability for sealing engagement to process equipment. Such containers have been termed “SMIF pods” (sealed mechanical interface) where the door closes an open bottom of the enclosure portion, or transport modules or FOUPS (Front Opening Unified Pod), where the door closes an open front. These containers are subjected to very demanding structural requirements and performance requirements. For example, they must mechanically latch by robotic or manual means and must of course provide exceptional isolation, such as being hermetically or near hermetically sealable simply by closing the door. For containers for 300 mm wafers that are utilized in fabs, front opening modules are being utilized. Conventional seals for both SMIF pods and transport modules have been relatively simple elastomeric seals that are simply compressed between the door and enclosure portion in an axial direction to provide the seal. As such, the seal contact with the door is aligned with the seal contact with the door frame. Such sealing, particularly where polycarbonate is the contacted by the elastomeric seal, tend to stick excessively and provide inconsistent opening, reduced life expectancy of the seal and inadequate sealing.

Better performing and longer lasting seals are needed for wafer containers and particularly the containers for larger wafers.

SUMMARY OF THE INVENTION

The substrate container of the present invention provides a magnetic seal or gasket between a door and an enclosure portion. The magnetic seal is formed around the periphery of a door and a door frame by utilization of a magnetic field between the door and the enclosure. The magnetic field is created by a magnet as part of at least of two opposing sealing parts. The door comprises one sealing part on the periphery of the door and the other cooperating part is on the door frame portion of the enclosure. In preferred embodiments, one part comprises a flexible or elastomeric gasket with a magnet or magnetic material therein. The second part has an opposing surface preferably with either a metallic strip or another magnet preferably covered by or embedded in rigid plastic or an elastomeric material. These two surfaces sealing engage each other when the first and second parts are in close proximity, thereby providing a seal for the container. The door is preferably retained to the enclosure by a latch, so the magnetic field strength between the two portions of the magnetic gasket or seal need only be strong enough to create a seal. In a preferred embodiment the door to door frame engagement has a hard stop, preferably hard plastic to hard plastic at which point the sealing part comprising a flexible gasket, extends by way of magnetic attraction to the other sealing part accomplishing a sealing connection between the door and enclosure portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a bottom-opening wafer carrier according to the invention.

FIG. 2 is a perspective view of a front-opening wafer carrier according to the invention.

FIG. 3 is a of the inner surface of a door to a front-opening wafer carrier according to the invention.

FIG. 4 is a cross-sectional view of a portion of a door and door frame with a non-engaged seal according to the invention.

FIG. 4 a is a detailed perspective cut-away view of a portion of a door according to the invention.

FIG. 4 b is a detailed perspective cut-away view of a portion of a container portion according to the invention.

FIG. 5 is a cross-sectional view of a portion of a door and a door frame with an engaged seal according to the invention.

FIG. 6 is a cross-sectional view of a portion of a door and a door frame with an alternate seal according to the invention.

FIG. 7 is a cross-sectional view of a portion of a door and door frame of a SMIF pod with a non-engaged seal according to the invention.

FIG. 8 is a cross-sectional view of a portion of the door and the door frame of FIG. 7 with the door encountering a hard stop with the enclosure portion according to the invention.

FIG. 9 is a cross-sectional view of the portion of the door and the door frame of FIG. 8 with the first sealing part comprising a flexible gasket extending into a sealing engagement with a second sealing part.

DESCRIPTION OF PREFERRED EMBODIMENTS

Prior art FIGS. 1 and 2 show a bottom-opening SMIF pod 20 and a front-opening transport module or FOUP 30 respectively for which the invention is highly suitable. Each sealable enclosure has a enclosure portion 34 and a cooperating door 36. The SMIF pod 20 also has a separate wafer carrier 38 which is a H-bar carrier, well known in the art, which seats on the top surface 40 of the door 36. A plurality of wafer supports 39 are present in each of both substrate containers.

Each enclosure portion 34 and each enclosure has a top side 46, a front side 48, and a bottom side 50. In the SMIF pod the bottom side 50 is open for receiving the wafer carrier 38 and the door 36. In the transport module 30 the front side 48 is open and is closed by the door 36. A recessed lip 51 is located at the periphery of enclosure portion 34.

The doors have an inwardly facing side 52, an outwardly facing side 53, and a periphery 54 including four sidewalls 55. Each of the doors 36 comprise an enclosure 56 with an open interior 58 which contains a latching mechanism 60, a portion of which is shown in FIGS. 1 and 2. The latching mechanism includes a latching portion 62 which is extendable out of slots 66 to engage into latching portion receivers 68 located in the door frame portion 74 of the enclosure portion 34. Door guides 75, may be utilized to provide guidance of the door into the door frame 74. Such door guides are described in detail in U.S. Pat. No. 6,464,081 owned by the owner of this application. Said patent is incorporated herein by reference.

On the inside surface 54 of the door are wafer cushions 80 which provide a slightly biased constraint to the wafers when the door is in place. The cushions may be attached suitably at the connection points 82 with plastic snapin connectors or other suitable means known in the art. The door enclosure portion may be configured such that the only contact between these components is the seal to door frame engagement and the door guide to door frame contact. Alternatively, supplemental stop portions may be provided in the enclosure portion to allow the door to bottom out when the seal is appropriately flexed in an extended position. A portion of enclosure 56 is removed in FIG. 2 to disclose a portion of door-latching mechanism 66. This latching mechanism may operate as disclosed in U.S. Pat. No. 5,711,427 to David L. Nyseth and owned by the owner of the present invention. For the purposes of full disclosure, this patent is incorporated herein by reference.

FIGS. 4, 4 a, 4 b, 5, and 6 show sealing devices 100 in different configurations. Door 36 is inserted in an axial direction, the “z” direction on the x-y-z coordinate system, as indicated by arrow 69. This is also the direction in which wafers are inserted. Sealing device 100 has a first sealing part 102 attached to door 36 and a second sealing part 104 attached to container enclosure 34. First sealing part 102 of sealing device 100 includes a base 110, an extendable and flexible member 112, and engagement surface 114, and an embedded, preferably overmolded, magnet 116. Second sealing part 104 of sealing device 100 includes a base 120 and an overmolded ring 122. Overmolded ring 122 may be made of any material capable of magnetically being attracted to overmolded magnet 116, such as another magnet, a metal, or the like, that is, a magnetically attractable material. As illustrated in FIG. 4 b, the ring of magnetically attractable material 122 may be multiple pieces 123 overmolded into the container portion. Alternatively, at least one of first sealing part 102 and second sealing part 104 may be plastic magnets. First sealing part 102 and second sealing part 104 are positioned opposite each other so that they engage easily when in close proximity.

Overmolding in the context of wafer container components is illustrated in U.S. Pat. Nos. 6,871,741 and 6,808,668 both owned by the owner of this application. Such techniques are highly suitable to the sealing structure disclosed herein. Said patents are incorporated herein by reference.

Sealing device 100 engages when first sealing part 102 and second sealing part 104 reach a critical proximity, which is a function of the magnetic field strength. For example, when first sealing part 102 and second sealing part 104 are initially aligned, but not in close proximity, sealing device 100 is in a non-engaged state, as depicted in FIG. 4. As first sealing part 102 and second sealing part 104 are moved closer together, engagement surface 114 eventually engages sealingly with second sealing part 104 as depicted in FIG. 5. The magnetic field strength is strong enough to sealingly engage door 36 and enclosure portion 34, yet it is not so strong that door 36 may not be removed easily when door 36 is removed from enclosure portion 34. Door 36 is retained to enclosure portion 34 by door-latching mechanism 66, so the magnet field strength need not be strong enough to retain door 36, but only strong enough to provide an adequate seal. Preferably, there is a hard stop 115 defined such as a non-gasket door surface 117 contacting a non-gasket door frame surface 119. The surfaces comprising the hard stop are preferably positioned such that the first sealing 102 must extend to engage and seal with the second sealing part 104 when the hard stop is accomplished.

The placement of the overmolded magnet 116 and overmolded ring 122 may be reversed, as shown in FIG. 6. In this embodiment, first sealing part 102 is attached to container enclosure 34 and second sealing part 104 is overmolded directly within the door 36. Even though the positions of first sealing part 102 and second sealing part 104 are reversed, they otherwise function as described above for the configurations shown in FIG. 5 and FIG. 6.

Additionally, the magnet may be embedded and fixed with respect to one of the door and enclosure portion and the other of the door and enclosure portion may have the sealing part with an extendible portion and a magnetically attractable material attached or contained or embedded therein. Said magnetically attractable material may be a single piece, multiple discrete pieces, or multiple particles disbursed throughout the flexible sealing part.

In certain embodiments the two engagement surfaces may both be more rigid, with neither one being elastomeric, rather sufficient sealing being provided by, for example rigid plastic to rigid plastic contact, the plastics being similar or dissimilar. For examples, polycarbonates and fluoropolymers such as PFA (perfluoroalkoxy), ABS, PEEK and other plastics known to those in the art may be suitable. Additionally the sealing part can have an extendible elastomeric portion and a rigid plastic that contacts and seals with the cooperating surface.

In use, first sealing part 102 and second sealing part 104 function as gaskets and a cooperating sealing surface. The overmolded magnet 116 and overmolded magnetically attractable material 123 cause engagement surface 114 to engage sealing surface 127 of second sealing part 104 as a result of magnetic attractive forces. Flexible member 112 of first sealing part 102 stretches when engagement surface 114 is positioned close enough for sealing engagement with second sealing part 104 of sealing device 100. The magnetic attractive forces, however, are only so strong that the engagement surface 114 and second sealing part 104 may be readily uncoupled manually or by a robotic arm when door-latching mechanism 66 is uncoupled and door 36 is removed from enclosure portion 34.

Referring to FIGS. 7, 8, and 9, an embodiment in the context of a SMIF pod with a door 140 and container portion 142 are illustrated. The container base or door 140 has a first sealing part 144 that includes an elastomeric flexible gasket 146 with a base portion 147 positioned in a recess or slot 148 in the door. An extendable portion 149 may be configured as a bellows or other elongatable configuration. The first sealing part preferably embeds, such as by overmolding, a magnet 150. A sealing surface 152 faces the opposing sealing surface as the door and container portion are brought together. The first sealing part has a retracted position as illustrated in FIGS. 7 and 8 as well as an extended position and an engagement position as illustrated in FIG. 9. A hard stop 115 similar to that described with reference to FIGS. 4 and 5 is also present.

As illustrated in FIG. 6, the magnet or the magnetically attractable material may be directly embedded in the principle material comprising the container portion, the door frame, or door enclosure, such as polycarbonate. In such a case the “first sealing part” or “second sealing part” is an integral portion of the door or enclosure portion as opposed to being part of an assembly. In other embodiments, both the first sealing part and second sealing part can have extendible portions 149.

The container portion 158 has a second sealing part 160 comprising a sealing surface 162 and has magnetically attractable material 166 therein, preferably embedded therein such that only plastic is exposed.

The sealing components in this embodiment function as follows. In FIG. 7 the first sealing part, in particular the extendable portion is in it retracted state with a magnetic field 170 not having any magnetically attractable components therein. In FIG. 8, the container portion has been placed on the door such that the magnetic material of the second sealing part is within the magnetic field 170 of the first sealing part. This causes an extension of the first sealing part toward the second sealing part to the sealing engagement constituting as shown in FIG. 9. When the door is removed, or the container portion lifted, the extendable portion is at or near its maximum position such that the sealing surfaces separate after minimal separation of the door and container portion.

The main structural components of the enclosure portion, particularly the door frame, may be molded of rigid plastic such as polycarbonate. Similarly, the main structural portions of the door, particularly the peripheral portions 54, similarly may be molded from polycarbonate. The wafer guides may suitably be formed of an abrasion resistant composite plastic such as polyetheretherketone (PEEK) and polytetrafluorethylene (PTFE). The elastomeric seal may be formed of elastomers such as Viton®, available from the Dupont Corporation, or generic ethylenepropylenediene monomer or similar elastomeric materials.

The present invention may be embodied in other specific forms without departing from its spirit or essential attributes; the embodiments described are thus in all respects illustrative and not restrictive. The appended claims rather than to the foregoing description indicate the scope of the invention. 

1. A substrate container, the container comprising: an enclosure portion having an open side with a first periphery, a door frame therearound, said door frame having a first sealing part extending therearound; substrate supports within the enclosure portion; and a door having a second periphery sized for engagement with said door frame, said door having a second sealing part extending around the second periphery for sealingly engaging the first sealing part, the door comprising a latch mechanism for latching onto the door frame; one of the first sealing part and second sealing part comprising a magnet, the other of the first sealing part and second sealing part comprising a magnetically attractable material whereby force pulls together in a sealing engagement said first sealing part and said second sealing part.
 2. The substrate container of claim 1, wherein the first sealing part includes an elastomeric overmolded ferrous or steel strip and the second sealing part includes a magnet overmolded with elastomeric material.
 3. The substrate container of claim 2, wherein the second sealing parts comprises an extendible portion formed of the elastomeric material, the second part having an extended position and a retracted position.
 4. The substrate container of claim 1, wherein one of the first and second sealing portions has an extendible portion and said one has a position and an extended position a and wherein when the first part and second part are in the sealing engagement the one is in its extended position.
 5. The substrate container of claim 1, wherein the door and container portion have a hard stop with the door in the door frame and wherein said seating position the first and second parts are sealingly engaged and the second part is in the extended position.
 6. The substrate container of claim 3, wherein said door frame has a groove and wherein the first sealing part comprises a magnetic gasket and said magnetic gasket is disposed in said groove.
 7. The substrate container of claim 1, wherein at least one of the first and second sealing parts includes a plastic magnet.
 8. The substrate container of claim 1, wherein at least one of the first and second sealing parts includes a series of discrete overmolded magnets spaced at intervals around one of the first or second peripheries.
 9. The substrate container of claim 8, wherein the other of the first and second sealing parts includes a series of discrete overmolded metallic pieces around the first or second peripheries.
 10. A sealable container for containing wafers, the container comprising: an enclosure with a door frame defining an open side, wherein said door frame includes; a rectangular outwardly facing flat and radially extending sealing surface and a first elastomeric magnetic seal extending around said door frame; and a door comprising: an interior facing surface; a parallel exterior facing surface; four side surfaces proximate the interior facing side and the exterior facing side; a groove inset in the four sides and extending around said door; and a second elastomeric magnetic seal in the groove and extending around the door, the second magnetic seal, in cross section, having an inset portion positioned in the groove and an exposed portion extending outwardly therefrom, the exposed portion having a cross section with a base portion, a flexible portion, and a sealing surface in substantial alignment in a radial direction, the sealing surface protruding substantially axially toward the enclosure portion and the exposed door frame as the door is inserted into and removed from the door frame by moving axially in a direction transverse to the greater dimension of the second elastomeric seal.
 11. The substrate container of claim 10, wherein the first magnetic seal includes an elastomeric overmolded metallic strip and the second magnetic seal includes an elastomeric overmolded magnet.
 12. The substrate container of claim 10, wherein at least one of the first and second magnetic seals is a plastic magnet.
 13. The substrate container of claim 10, further comprising a door latch for attaching said door to said enclosure.
 14. The substrate container of claim 10, wherein at least one of the first and second magnetic seals includes a series of discrete overmolded magnets spaced at intervals around the first or second peripheries.
 15. The substrate container of claim 10, wherein at least one of the first and second magnetic seals includes a series of discrete overmolded metallic strips around the first or second peripheries.
 16. A method for sealing wafer containers, the method comprising the following steps: providing an enclosure defining a first periphery, said enclosure having a door frame around the first periphery, said door frame having a first magnetic gasket and a first door latch mechanism proximate the first periphery; and providing a door defining a second periphery sized for engagement with said door frame, said door having a second magnetic gasket around the second periphery for sealingly engaging the first magnetic gasket and further having a second door latch mechanism proximate the second periphery for engaging the first latch mechanism; and engaging the first latch mechanism with the second latch mechanism; and sealingly engaging the first magnetic gasket with the second magnetic gasket.
 17. The method of claim 16 wherein the first magnetic gasket includes an elastomeric overmolded metallic strip and the second magnetic gasket includes an elastomeric overmolded magnet.
 18. The method of claim 16 wherein at least one of the first and second magnetic seals is a plastic magnet.
 19. The method of claim 16, wherein at least one of the first and second magnetic seals includes a series of discrete overmolded magnets spaced at intervals around the first or second peripheries.
 20. The method of claim 16, wherein at least one of the first and second magnetic seals includes a series of discrete overmolded metallic strips around the first or second peripheries. 